Apparatus for correcting gears



Sqfl-6,193Z A.B.REDNER L876J67 APPARATUS FOR CORRECTING GEARS Filed Aug. 23, 1929 v as I. I

I /7Z Ze/25./2 J22er C) I I 1 BY 410L614 X? I 2mm 1am l 27 ATTORN EY-S' Patented Sept. 6, 1932 UNITED STATES PATENT ALLEN B; REDNER, OF LANSINQ MIGHIGAN, ASSIGNOR TOqREO -MO'I0R CAR COMPANY,

OF LANSING, MICHIGAN, A CORPORATION OF JVIICHIGAN APPARATUS FOR comm-norms GEARS Application filed. August 28, 1929. Serial No. 389,023.

This invention relates to a method and apparatus for correcting gears and; more particularly to improvements therein designed to correctly modify geometrically correct gears.

In designing gears the desired size and ratio is first determined and then the exact proportions, pitch, face, pressure angles and other details are definitely geometricallydetermined. Theoretically, gears generated from these geometrically correct specifications should operate perfectly without appreciable noise or vibration.

In the present day manufacture of gears it is quite generally the practice to employ any one of several standard types of gear cutting machines, one of which is commercially known as the Gleason machine. In generating spiral pinion type of gears with the tice today to use a selected standard size finishing cutter. These finishing cutters are furnished in a number of standard sizes in i which the cutting angles vary approximate- 1y 10' one from the other, starting, vfor instance, with cutter known as No. 3%, having cutting angles respectively of 13? '55 and 15 5 and ending with cutter known as No. 12 with cutting. angles respectively of 12 and 16 In the group of cutters just given as an example the angles specified are designed for generating a gear having a Mi mean pressure angle. It is the practice to furnish another set of cutters'having the cutting angles designed for generating gears having, for instance, a 20 mean pressure angle. I p

However, in actual practice, ithas been found that while these standard finishing cutters are geometrically designed to generate geometrically correct gears, certain interference occurs in the meshing of the gears,

which results in objectionable noise. It is therefore one of the primary objects of this Gleason-machine itis the standard pracdrawing,

invention to provide a method and means for correcting the shape of the tooth generated in the manner described above, so as to eliminate the aforesaid interference and produce a noiseless smooth running gear.

The several objects and advantages of the present invention, together with the method and means for carrying the same into execution will be made more apparent as this de scription proceeds, especially when considered in connection with the accompanying drawing wherein 5 Figure 1 is a fragmentary perspective view of a portion of a Gleason gear cutting machine designed to generate spiral beveled pinions; p

v Figure 2 is a sectional elevational view of a spiral beveled pinion generated by the machine illustrated in Figure 1;

Figure 3 is an enlargedfragmentary semidiagrammatic view showing several teeth of a pinion meshing with a gear;

Figure 4 is a perspective view of one of the cutters; and

Figure 5 is a plan view'of the cutter.

Referring now more particularly to the wherein like reference characters it will be noted that the problem generally is that of generating a spiral beveled pinion 10. (See Figures 1 and 2.) I In order that the invention may be fully understood the particular manner in which it is practiced is described in detail in connection withthe generating of a spiral bevel pinion, but obviously the invention is applicable in the manufacture of various other types of gears.

Inasmuch as certain dimensions and other figures hereafter to be mentioned may vary in direct relation to the specifications of the gear being generated, I will give herein. the particular specifications of the gear with respect to which this invention is being described.

indicate like parts,

Root angle 11 20 of the other geometrical fundamentals of the Pitch angle 12 15 gear but rather from an interfering engage- F ace angle 15 19 ment of portions of the tooth falling without 12 teeth .487 pitch the sphere of the principal geometrical cal- Pressure angle 14 30 culations. Gear to set has 53 teeth For example, by reference to Figure 3, it

L. H. spiral to be cut with #6 Gleason cutter.

Pitch depth .250 Working depth .349 Full depth .888 Spiral angle 29 37 Blank dia 2.952

The Gleason type of gear cutting machine fragmentarily illustrated in Figure 1 is well known in this art and is standard equipment for a large proportion of gear manufacturers. Therefore, a fuller disclosure and detailed description is deemed unnecessary. Suflice it to say that the machine includes a rotary cutter head 11 upon which is mounted a plurality of cutters 12 which are rotated an d otherwise properly manipulated with respect to the pinion 10, so as to generate the teeth thereof. The pinion is supported by its shank portion 13 (see Figure 2) in a chuck or holder 14 and properly rotated and periodic-ally indexed as is well known in connection with this type of machine.

By reference to Figure Sit will be noted that there is semi-diagrammatically"illustrated in cross section several of the teeth of pinion 10, these teeth being shown meshing with several teeth of a driven gear 15. In gearing which is geometrically correctly designed it is customary to have'three teeth constantly in contact, and in Figure 3 such a condition exists, and hereafter in this description particular reference will be made to teeth A, B and O of the driving pinion 10, it being understood, however, that the conditions and corrections to be described in connection with these three teeth exist with respect to all of the remainingteeth of the pinion.

In Figure 3 the teeth A, B and C are shown in full lines as they come from the gear cutting machine illustrated in Figure 1. These teeth, as heretofore mentioned, are geometrically correct, as to root, pitch and face angle and all other conditions with respect to a gear of this type. It has been found in practice, however, that interference results in the meshing of the teeth'of the driving pinion with those of the driven gear. It was discovered that this interference occurred at the beginning of the period of engagement of the pinion tooth and at the end of this period of engagement. The engagement of the tooth during the period intermediate the beginning and end causes no interference. It was ascertained, therefore,

, that the interference resulted not from. the

incorrect pressure angle, pitch circle or any will be seen that driving pinion 10 is moving in the direction of the arrow and driving the driven gear 15. The reference characters 16, 17 and 18 indicate respectively the driving side of teeth A, B and C of the pinion 10. The reference characters 19, 20 and 21 indicate respectively the back or reverse sides of the teeth A,B and C. The reference character 22 indicates the pitch circle of the pinion and gear, and from its position it will be noted that tooth B is correctly meshing with the corresponding teeth on the driven gear. However, it will be noted that that portion 23 of tooth A within the addendum circle and adjacent the face of the tooth is interfering with the adjacent surface of tooth D of the driven gear. This interference acts to hold the driven gear back, and immediately that this interference is removed and the driven gear released an impact results between the driving side of tooth B of the pinion'and tooth F of the gear. Moreover, as the tooth D of the driven gear comes into mesh with tooth AA of the pinion, an interference results between the face of tooth D of the driven gear and the tooth AA adjacent the root thereof and adjacent the dedendum circle. However, as previously pointed out, tooth B correctly meshes with the teeth E and F of the gear 15. Because of the interference betweeen the pinion teeth A and AA. and the gear tooth D there is also interference'between the pinion tooth C and the gear teeth F and G. Part of this interference is betweeen the driving side of'tooth C at 24: adjacent the face thereof and within the addendum circle and partly between the reverse side of the tooth adjacent the root thereof with the gear tooth F and within the dedendum circle.

As heretofore mentioned, this interference causes the driven gear to be alternately held and released, with the result that there is an impact between the teeth of the driving pinion and the driven gear. Particularly in high speeds this results in a noise and vibration which is objectionable.

In accordance with the present invention I propose to relieve the driving side of each tooth principally within the dedendum circle, and the reverse side of each tooth principally within the addendum circle. The fundamental geometrically correct angles and other essentials of the gear are in no wise materially affected. However, the relief given at the points justmentioned eliminates the objectionable interference heretofore pointed out and permits the gears to operate this figure it will be noted that each tooth is relieved on its driving side as indicated by the dotted line 25, and on its reverse side as indicated by the dotted line 26.

Obviously various means might be employed for effecting these results, such for instance as properly manipulating the cutting head of the heretofore mentioned Gleason gear cutting machine; However, in accordance with this invention, I propose a simple, eflicient and practical means for accomplishing this result without any modification or adjustment of the gear cutting machine itself. In accordance with my invention I propose modifying the finish cutters 12 in the manner most clearly illustrated in Figures 4 and 5. Ingenerating a gear of the size and character heretofore mentioned, it is customary to employ what is known as a Gleason cutter No. 6 For cutting a mean pressure angle of 14 a No. 6% cutter has a cutting angle of 13 and 25' for cutting the driving side of the tooth, and a cutting angle of 15 and 35 for cutting the reverse side of the tooth. A No. 7 cutter has corresponding cutting angles of 18 and 15 and 15 and 4.5, a difference of 10 in each cut ting angle.

In practice I have found that the best results are obtained by relieving the tooth on each side approximately 5 and 42 or 48", thus correcting the pressure angle. to that extent. A number 6 Gleason standard cutter does not remove sufiicient material and a number 7 Gleason standard cutter removes too much material to accomplish the desired result. I therefore take a standard 6 cutter and modify the cutting edge 27 thereof by removing, forinstance by grinding, approximately 2, starting from the point or outer edge 28 and extending to the base or inner edge 29. Thus the cutting edge after modification is substantially as indicated by dotted lines in Figures A and 5, although this illustration is somewhat exaggerated for the purpose of clearness. The cutters employed in generating the driving side of the teeth are modified in this manner, whereas the cutters employed in generating the reverse side of each tooth are modified in a reverse manner, the edge being changed two degrees, tapering from the base to the outer edge.

In this manner the cutter for the driving side is hooked and the cutter for the reverse side of the tooth is dragged. When the cut-' ters, modified as indicated, are associated with a standard Gleason machine, as illustrated in Figure 1, the teeth are generated as indicated by dotted lines in Figure 3.

While one illustrative embodiment of the invention has been described and claimed herein somewhat in detail, it will be readily apparentto those skilled in this art that various changes in many of the nonessential details may be resorted to without departing from the spirit and scope of this invention, and to this end reservation is made to make such changes as may'come within the purview of the accompanying claims.

I cla1m as my mventioni' 1. A Gleason finish cutter modified from Gleasons standard practice of between 13 and 16 cutting angle by altering the cutting edge approximately two degrees.

2. A cutter for generating spiral bevel gears comprising a face mill having a plurality of teeth arranged circumferentially thereof, each tooth having its cutting edge modified from standard Gleason practice by having a cutting edge hooked approximately two degrees.

3. A cutter for generating spiral bevel gears comprising a face mill having a plu rality of teeth arranged circumferentially thereof, each tooth being a standard Gleason cutter No. 6 normally having a cutting.

angle between 13 and 16 modified by having the cutting angle hooked approximately two degrees. r

4:. A cutter for generating spiral bevel gears comprising a face mill having a plurality of teeth arranged circumferentially thereof, each tooth being a standard Gleason cutter No. 6 normally having an angle of approximately 13 and 25 modified by hav- 7 ing the cutting edge inclined at an angle approximately two degrees greater than the normal angle for the cutting edge,

In testimony whereof I afiix my signature.

ALLEN B. REDNER. 

